A communications network comprises two or more nodes and the physical link(s) between the nodes. On a packet-switched communications network, e.g., the Internet, communications are in the form of discrete units of information known as packets. A typical communication on the Internet is between two endpoint nodes generating and sending packets to each other via one or more links and zero, one, or more intermediate nodes.
The Internet is a digital packet-switched network that uses the four-layer Internet Procotol suite for the generation and processing of packets. The Internet Protocol suite (IP suite) is defined in Internet Engineering Task Force (IETF) Request for Comment (RFC) 1122. The lowest layer of the IP suite is the link layer (e.g., Ethernet), followed by the network layer (e.g., Internet Protocol (IP)), the transport layer (e.g., Transport Control Procotol (TCP)), and, highest, the application layer (e.g., Simple Mail Transport Protocol (SMTP) or Hypertext Transfer Protocol (HTTP)). The term “session” refers to a communication between two nodes at a particular layer, e.g., a link-layer session or a transport session. The term “conversation” refers to a transport-layer session or an application-layer session or a combined transport/application layer session. The two nodes in a conversation are referred to as correspondent nodes.
The establishment of a session at a particular layer typically requires that all lower layers have established a session. For example, establishing a conversation typically requires sessions to be established at the transport, network, and link layers. Conversely, terminating a session at a particular layer typically terminates all sessions at higher layers, e.g., terminating an IP session (network layer) typically terminates transport-layer sessions and application-layer sessions (i.e., conversations).
A typical node connects to the Internet via an access network. A typical access network comprises a router that manages an IP-address range also known as a subnet. A router is a network node that retransmits received packets towards one or more other network nodes. A node connects to the Internet by first establishing a link-layer (e.g., Ethernet) connection with the access-network router. Typically, the router then assigns the next available address from the subnet to the node. The node then can establish transport-layer sessions and conversations with other nodes on the Internet.
Moving a node within an access network typically does not terminate the node's conversations. For instance link-layer protocols, such as the Address Resolution Protocol (ARP), allow a node to change its link-layer address without disturbing higher-layer protocols. In other words, a typical node is able to change its link-layer session without disturbing its network-layer, transport-layer, or application-layer sessions. This ability is known as micro-mobility.
Macro-mobility is the ability to change a network-layer session without disturbing transport-layer and application-layer sessions. The most common network-layer protocol in use today, IP version 4 (IPv4), does not provide macro-mobility. IPv4 is defined in IETF RFC 791. Thus, when the network-layer session on an IPv4 node is interrupted, all of the node's conversations are terminated.
A response to the lack of macro-mobility in IPv4 has been new network-layer protocols that support macro-mobility. One class of the new network-layer protocols is referred to as Mobile IP (MIP). MIP protocols include Mobility Support in IP version 4 (MIPv4), defined in IETF RFC 3344, and Mobility Support in IP version 6 (MIPv6), which is defined in IETF RFCs 3775 and 4866.
Both MIPv4 and MIPv6 provide macro-mobility through triangular routing. Triangular routing has a number of disadvantages, such as increased complexity, increased packet overhead, and exclusion of more-efficient routes.
In U.S. patent application US 2010/0135301, alternative methods for implementing macro-mobility in an IP network are described, which avoid triangular routing, and which are referred to as NMIP (Not Mobile IP). Not Mobile IP (NMIP) is an end-host-based signaling protocol that enables Mobile Nodes (MNs) and Correspondent Nodes (CNs) to update each other with IP address changes at mobility events and to reroute traffic for established TCP, UDP, ESP, etc. . . . sessions using newly obtained IP addresses without breaking connections. Backward compatibility is provided by a mechanism in which a first node which sends an address update to a second node, and does not receive feedback before a address-update-reply timer expires, periodically sends address-update (related) messages to the old NMIP mobility router, which behaves as a MIP agent.
There is a need for alternative solutions in the NMIP framework which can provide backward compatibility with network nodes which are not NMIP enabled/compliant.